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hot water, then with- warm dilute caustic soda and water again.
Yield, 10 — 12 grams.

Sublimation.— A portion of the dry substance may be
purified by sublimation. It is placed (2—3 grams) on a large
watch-glass, which is heated on the sand-bath over a very small
flame. The watch-glass is covered with a sheet of filter paper,
which is kept flat by a funnel placed above. After five minutes
or so pale yellow, needle-shaped crystals of anthraquinone will
have sublimed on to the filter paper.

,CHV                                                /COX

C0H '   I    \CflH4 + 2Cr03 + 6C,H4Oa = CflH4<       >CrtH.,+
XCH/                                               XCO"

Properties. — Yellow needles: m. p. 277 ; sublimes at 250 ;
b. p. 382" ; insoluble in water, soluble in acetic acid, less soluble
in benzene and other organic solvents.

Reaction. — Add a little dilute caustic soda to a small quantity
of anthraquinone, and then a little zinc dust. On heating to
boiling, an intense red colouration is produced, which disappear^

on shaking.    Sodium oxanthranolate, C<5H.,                .

formed,   which   oxidises   in   the   air  to   anthraquinone.
Appendix, p. 316.


Anthraquinone /^monosulphonate of Sodium,
CGH 4/Ł°\C0H3.SOaNa + H,O

Graebe, Liebermann, Annalcn, 1871,160, 131 ; A. G. Perkm,
Private communication.
30 grms. anthraquinone.
30     „     fuming sulphuric acid (40 per cent. SO;.).1
The 40 per cent, fuming sulphuric acid is removed from tin;
bottle by cautiously melting it in a sand-bath, and it is then
weighed, out in a flask (Ł litre). The anthraquinone is added,
and the flask attached by a cork to an air-condenser. Tin.?
1 As fuming sulphuric acid is difficult to keep In an ordinary stoppered butt I**
without absorbing moisture, it is advisable to coat the stopper with a layer Ťyf
paraffin wax, and a substantial covering of plaster of Paris above this.